HOUSTON – A critical device at the center of an investigation into the Gulf oil rig explosion didn't undergo a rigorous recertification process in 2005 as required by federal regulators, a worker responsible for maintaining the equipment told investigators Wednesday.

Mark Hay of rig-owner Transocean said the blowout preventer — designed to prevent a spill in the case of an explosion — was not recertified because it was being constantly maintained. Recertifying the five-story device requires completely disassembling it out of the water and can take as long as three months to complete.

The device — which may be lifted from the seafloor a mile below the water's surface in the coming days — failed following the rig explosion. After the blowout, some 206 million gallons of oil spewed into the Gulf until mid-July, when a temporary cap stopped the flow. A permanent fix is expected to be put in place after Labor Day.

The blowout preventer will be key to the investigation into the April 20 explosion that killed 11 people and caused the biggest oil spill in U.S. history.

Testimony from BP and Transocean officials showed the device had not been recertified according to a three- to-five year timetable laid out by federal regulators; repairs were not always authorized by the manufacturer, Cameron; and in the days after the explosion confusion reined about changes to the equipment, delaying attempts to close the well.

Hay could not say how much it would have cost to recertify the blowout preventer, but said he knew it was functioning because he personally oversaw its maintenance.

The device underwent tests to ensure it was working, he told the joint investigation by the U.S. Coast Guard and the Bureau of Ocean Energy Management, Regulation and Enforcement.

The device, he said, had undergone a maintenance overhaul in February as it was being moved to the Deepwater Horizon to be placed over BP's well.

When asked if he had any doubts April 20 that the device was in full working order, Hay said: "No, sir."

He also detailed getting approval from Transocean's headquarters before making modifications to the device, and in at least one case making a change requested by BP.

Harry Thierens, BP's vice president for drilling and completions, told the federal panel documents detailing the changes to the equipment were not readily available, a waste of critical time after the explosion.

It took between 12 hours and 24 hours to get drawings of changes made to a locking system, Thierens said, and there were other changes and questions.

"If that time had not been necessary a faster response" could have been possible, Thierens said.

During this time, Thierens kept copious handwritten notes in a logbook. Before each item he wrote the hour in military time, then noted key moments from conversations he had with personnel from BP, the operator of the well, and with people from other companies, including Transocean.

Thierens worked closely with Transocean employees to try to activate the preventer with undersea robots beginning four days after the explosion and until it became clear — sometime in early May — that the device was not going to work.

At some point in his log notes, Thierens questions whether Transocean personnel had made changes according to their own protocols. "My concern right now is that Transocean made an ... uncontrolled change on the rig."

It later became apparent that there were a variety of other problems with the device, including pipes being run to different places. Thierens and the other workers trying to shut in the device suddenly learned that after hours of working to build up pressure to one area they were actually doing the work to another part of the device.

"I spoke frankly about the seriousness of this issue and quite frankly was astonished that this could have happened," Thierens wrote. "When I heard this news I lost all faith in the BOP stack plumbing," he added, referring to the device by its acronym.

When pressed, however, Thierens admitted none of it mattered because the blowout preventer didn't work, even when all the other problems were addressed.

Retired Coast Guard Adm. Thad Allen, the government's point man on the spill response, declined to give a specific timeline on when the blowout preventer would be raised from the seafloor.

Meanwhile, the chairmen of the presidential panel investigating the spill expressed surprise and disappointment that the Obama administration didn't consult senior U.S. environmental officials before announcing plans to expand offshore drilling before the accident.

The exchange suggests that a focus of the federal investigation will be the degree to which federal scientists were consulted in oil and gas decisions before the explosion. Federal law leaves the decision on where and when to drill to the Interior Department Secretary, who releases plans every five years.

Also Wednesday, BP said it was deploying new technology that it believes will provide a steady stream of data about water quality in the Gulf.

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Associated Press writers Dina Capiello in Washington and Harry R. Weber in New Orleans contributed to this report.